This invention relates to polyols useful for preparing water blown polyurethane foams. This invention particularly relates to Mannich polyols useful for preparing water blown polyurethane foams.
It has long been known to prepare rigid polyurethane foams by the reaction of a polyisocyanate with a hydroxyl-terminated polyester or poly(oxyalkylene)ether having a hydroxyl number within the range of from about 350 to about 900. One group of polyols useful for preparing such foams includes the nitrogen-containing polyols described in U.S. Pat. Nos. 3,297,597, 4,137,265, and 4,383,102 ('102). The nitrogen containing polyols which are prepared by alkoxylation of the reaction product of a phenol, alkanolamines and formaldehyde, such as those disclosed in '102 above, shall be hereinafter referred to as Mannich polyols. It has been reported in the literature that polyurethane foam prepared from these polyols is characterized by a greater inherent fire retardancy and good dimensional strength when extraneous fire retardants are employed.
One area of use for such polyols has been in spray foams systems used in roof and pipe insulation applications. The equipment normally used for the industrial application of sprayed urethane foam uses "double acting" positive displacement pumps which have the advantage of supplying an accurate component ratio in a continuous stream. A major disadvantage of this metering system is that it will function reliably only if the B-component has a viscosity of less than 1,000 centipoise at ambient temperature. At higher viscosities, cavitation can occur on the B-component side, resulting in a component ratio change which can affect the foam product quality.
Typically, in the past, the formulations used to prepare spray systems have included halocarbon blowing agents. In the present, the use of many of the traditional blowing agents have been discontinued, or phased out, because of the belief that they contribute to the destruction of the ozone layer which limits the amount of ultraviolet radiation which penetrates the atmosphere. This has resulted in a search for alternative blowing agents such as water.
While water is a useful blowing agent in many types of polyurethane foam, it does not have all of the properties of the halocarbon blowing agents which it has replaced. For example, one disadvantage of water as a blowing agent in polyol formulations including Mannich polyols is water does not reduce the viscosity of Mannich polyols as effectively as halocarbon blowing agents. As stated above, attempting to make foams with formulations which are too high in viscosity can cause problems with some kinds of foam making equipment. Therefore, it would be desirable in the art of preparing water blown polyurethane foams from formulations including Mannich polyols to use an ultra low viscosity Mannich polyol of sufficiently low viscosity to avoid handling problems such as cavitation problems with foam forming equipment.